Complementary Control Valve Sequence

The first type of control valve sequencing is a mode where two valves serve to proportion a mixture of two fluid streams, such as this example where base and pigment liquids are mixed together to form colored paint:

Complementary Control Valve Sequence

control valve sequencing

Both base and pigment valves operate from the same 3 to 15 PSI pneumatic signal output by the I/P transducer (AY), but one of the valves is Air-To-Open while the other is Air-To-Close.

The following table shows the relationship between valve opening for each control valve and the controller’s output:

valve opening for each control valve

An alternative expression for this split-range valve behavior is a graph showing each valve opening as a colored stripe of varying width (wider representing further open).

For this particular mode of split-ranging, the graph would look like this:

Valve split-range behavior

With this form of split-ranging, there is never a condition in the controller’s output range where both valves are fully open or fully shut. Rather, each valve complements the other’s position (Note 1).

Note 1 : In mathematics, a “complement” is a value whose sum with another quantity always results in a fixed total. Complementary angles, for instance, always add to 90 deg (a right angle).

An alternative to complementary valve sequencing in a process where two fluid streams mix (or diverge) is to use one three-way valve (Note2) rather than a pair of two-way valves:

Note 2 : Also known as a mixing valve or a diverting valve, depending on how it is applied to process service.

Split Range Valve Sequence Diagram

A photograph of a three-way globe valve mixing hot and cold water to control temperature is shown here:

three-way globe valve

Also Read : Control Valve Interview Questions

Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address

Leave a Comment